The Iberian Pyrite Belt: a mineralized system dismembered by voluminous high-level sills

The Iberian Pyrite Belt is a world-ranking massive sulphide province in which a reassessment of the palaeovolcanology has dramatically changed understanding of the source of metals and mechanism of ore formation. In the northern sector, the deposits are hosted by a sill–sediment complex in which more than 90% of the sills post-date the sulphide sheets. Because of a very high sill/sediment ratio, these late intrusions dominate the host succession and have severely disrupted the post-mineralization configuration thus obscuring the true genetic relationships. For example, some oxide deposits have been separated by hectometric sills from sulphide deposits they originally capped, creating seemingly totally independent mineralizing systems. In addition, stratiform sulphide sheets without underlying stockworks are not necessarily allochthonous. An early timing for the mineralization with respect to volcanism means that metals had to be predominantly sourced from the sedimentary basin and the continental crust below the volcanogenic sequence.